//
// Created by user on 2022/2/22.
//

#include <vector>
using namespace std;

int peakIndexInMountainArray(vector<int>& arr) {
    int left = 0, right = arr.size() - 1;
    while (left < right) {
        int mid = left + (right - left) / 2;
        if (arr[mid] < arr[mid + 1]) {
            left = mid + 1;
        } else {
            right = mid;
        }
    }
    return left;
}